Monomer, polymer, resist composition, and patterning process

ABSTRACT

A polymer for resist use is obtainable from a monomer having formula (1) wherein R 1  is H, CH 3  or CF 3 , R 2  and R 3  are a monovalent hydrocarbon group, R 4  to R 9  are hydrogen or a monovalent hydrocarbon group, R 10  is a monovalent hydrocarbon group or fluorinated hydrocarbon group, A 1  is a divalent hydrocarbon group, k 1  is 0 or 1, and n 1A  is 0, 1 or 2. A resist composition comprising the polymer displays a high dissolution contrast during organic solvent development.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2013-032716 filed in Japan on Feb. 22, 2013,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a monomer useful as a starting reactant forfunctional, pharmaceutical and agricultural chemicals, a polymercomprising recurring units derived from the monomer, a resistcomposition comprising the polymer, and a pattern forming process usingthe resist composition. The monomer is useful for the preparation of apolymer that finds use as a base resin in a resist composition which issubject to a pattern forming process involving exposure of resist film,deprotection reaction with the aid of acid and heat, and development inan organic solvent to form a negative tone pattern in which theunexposed region is dissolved and the exposed region is not dissolved.

BACKGROUND ART

The process that draws attention under the current circumstances is adouble patterning process involving a first set of exposure anddevelopment to form a first pattern and a second set of exposure anddevelopment to form a pattern between the first pattern features. Anumber of double patterning processes are proposed. One exemplaryprocess involves a first set of exposure and development to form aphotoresist pattern having lines and spaces at intervals of 1:3,processing the underlying layer of hard mask by dry etching, applyinganother layer of hard mask thereon, a second set of exposure anddevelopment of a photoresist film to form a line pattern in the spacesof the first exposure, and processing the hard mask by dry etching,thereby forming a line-and-space pattern at a half pitch of the firstpattern. An alternative process involves a first set of exposure anddevelopment to form a photoresist pattern having spaces and lines atintervals of 1:3, processing the underlying layer of hard mask by dryetching, applying a photoresist layer thereon, a second set of exposureand development to form a second space pattern on the remaining hardmask portion, and processing the hard mask by dry etching. In eitherprocess, the hard mask is processed by two dry etchings.

As compared with the line pattern, the hole pattern is difficult toreduce the feature size. In order for the prior art method to form fineholes, an attempt is made to form fine holes by under-exposure of apositive resist film combined with a hole pattern mask. This, however,results in the exposure margin being extremely narrowed. It is thenproposed to form holes of greater size, followed by thermal flow orRELACS® method to shrink the holes as developed. However, there is aproblem that control accuracy becomes lower as the pattern size afterdevelopment and the size after shrinkage differ greater and the quantityof shrinkage is greater. With the hole shrinking method, the hole sizecan be shrunk, but the pitch cannot be narrowed.

It is then proposed in Non-Patent Document 1 that a pattern ofX-direction lines is formed in a positive resist film using dipoleillumination, the resist pattern is cured, another resist material iscoated thereon, and a pattern of Y-direction lines is formed in theother resist film using dipole illumination, leaving a grid linepattern, spaces of which provide a hole pattern. Although a hole patterncan be formed at a wide margin by combining X and Y lines and usingdipole illumination featuring a high contrast, it is difficult to etchvertically staged line patterns at a high dimensional accuracy. It isproposed in Non-Patent Document 2 to form a hole pattern by exposure ofa negative resist film through a Levenson phase shift mask ofX-direction lines combined with a Levenson phase shift mask ofY-direction lines. However, the crosslinking negative resist film hasthe drawback that the resolving power is low as compared with thepositive resist film, because the maximum resolution of ultrafine holesis determined by the bridge margin.

A hole pattern resulting from a combination of two exposures of X- andY-direction lines and subsequent image reversal into a negative patterncan be formed using a high-contrast line pattern of light. Thus holeshaving a narrow pitch and fine size can be opened as compared with theprior art.

Non-Patent Document 3 reports three methods for forming hole patternsvia image reversal. The three methods are: method (1) involvingsubjecting a positive resist composition to two double-dipole exposuresof X and Y lines to form a dot pattern, depositing a SiO₂ film thereonby LPCVD, and effecting O₂-RIE for reversal of dots into holes; method(2) involving forming a dot pattern by the same steps as in (1), butusing a resist composition designed to turn alkali-soluble andsolvent-insoluble upon heating, coating a phenol-base overcoat filmthereon, effecting alkaline development for image reversal to form ahole pattern; and method (3) involving double dipole exposure of apositive resist composition and organic solvent development for imagereversal to form holes.

The organic solvent development to form a negative pattern is atraditional technique. A resist composition comprising cyclized rubberis developed using an alkene such as xylene as the developer. An earlychemically amplified resist composition comprisingpoly(tert-butoxycarbonyloxy-styrene) is developed with anisole as thedeveloper to form a negative pattern.

Recently a highlight is put on the organic solvent development again. Itwould be desirable if a very fine hole pattern, which is not achievablewith the positive tone, is resolvable through negative tone exposure. Tothis end, a positive resist composition featuring a high resolution issubjected to organic solvent development to form a negative pattern. Anattempt to double a resolution by combining two developments, alkalinedevelopment and organic solvent development is under study.

As the ArF resist composition for negative tone development with organicsolvent, positive ArF resist compositions of the prior art design may beused. Such pattern forming processes are described in Patent Documents 1to 3. These patent documents disclose resist compositions for organicsolvent development comprising a copolymer of hydroxyadamantanemethacrylate, a copolymer of norbornane lactone methacrylate, and acopolymer of methacrylate having acidic groups including carboxyl,sulfo, phenol and thiol groups substituted with two or more acid labilegroups, and pattern forming processes using the same.

Further, Patent Document 4 discloses a process for forming a patternthrough organic solvent development in which a protective film isapplied onto a resist film. Patent Document 5 discloses a topcoatlessprocess for forming a pattern through organic solvent development inwhich an additive is added to a resist composition so that the additivemay segregate at the resist film surface after spin coating to providethe surface with improved water repellency.

The positive development system involving deprotection reaction togenerate a carboxyl group and subsequent neutralization reaction withaqueous alkaline developer to improve a dissolution rate achieves a highdissolution contrast in that the dissolution rate differs between theunexposed and exposed regions by a factor of more than 1,000. Incontrast, the negative development system via organic solventdevelopment provides a low contrast because the dissolution rate in theunexposed region due to solvation is low, and the dissolution rate thusdiffers between the unexposed and exposed regions by a factor of lessthan 100. For the negative development system via organic solventdevelopment, it is desired to seek for a novel material which can offera high dissolution contrast.

CITATION LIST

-   Patent Document 1: JP-A 2008-281974-   Patent Document 2: JP-A 2008-281975-   Patent Document 3: JP 4554665-   Patent Document 4: JP 4590431-   Patent Document 5: JP-A 2008-309879-   Non-Patent Document 1: Proc. SPIE Vol. 5377, p. 255 (2004)-   Non-Patent Document 2: IEEE IEDM Tech. Digest 61 (1996)-   Non-Patent Document 3: Proc. SPIE Vol. 7274, p. 72740N (2009)

DISCLOSURE OF INVENTION

The organic solvent development is low in dissolution contrast, ascompared with the positive resist system adapted to be dissolved inalkaline developer when deprotection reaction takes place to produceacidic carboxyl or phenol groups. Specifically, in the case of alkalinedeveloper, the alkali dissolution rate differs more than 1,000 timesbetween unexposed and exposed regions, whereas the difference in thecase of organic solvent development is at most 100 times, and only about10 times for certain materials. No sufficient margin is available. Inthe case of aqueous alkaline development, the dissolution rate isimproved by neutralization reaction with carboxyl groups. In the case oforganic solvent development with no accompanying reaction, thedissolution rate is low because dissolution is solely due to solvation.It is necessary not only to improve the dissolution rate of theunexposed region, but also to reduce the dissolution rate of the exposedregion that is a remaining portion of resist film. If the dissolutionrate of the exposed region is high, the thickness of the remaining filmis so reduced that the underlying substrate may not be processed byetching through the pattern as developed. Further it is important toenhance the gradient or gamma (γ) at the dose corresponding todissolution/non-dissolution conversion. A low γ value is prone to forman inversely tapered profile and allows for pattern collapse in the caseof a line pattern. To obtain a perpendicular pattern, the resist musthave a dissolution contrast having a γ value as high as possible.

An object of the invention is to provide a photoresist composition whichdisplays a high sensitivity and a high dissolution contrast duringorganic solvent development. Specifically, an object of the invention isto provide a monomer, a polymer prepared from the monomer and suited foruse in photoresist compositions, a resist composition comprising thepolymer as a base resin, and a pattern forming process using the resistcomposition.

The inventors have found that a resist composition comprising a polymerobtained from a monomer having the general formula (1) as a base resinis improved in many factors including dissolution contrast duringorganic solvent development to form negative patterns, size uniformityof hole patterns formed via positive/negative reversal, exposurelatitude, LWR and MEEF of line-and-space patterns, and DOF margin oftrench patterns.

In a first aspect, the invention provides a monomer having the generalformula (1).

Herein R¹ is hydrogen, methyl or trifluoromethyl, R² and R³ are eachindependently a straight, branched or cyclic monovalent hydrocarbongroup of 1 to 10 carbon atoms, R² and R³ may bond together to form aring with the carbon atom to which they are attached, R⁴ to R⁹ are eachindependently hydrogen or a straight, branched or cyclic monovalenthydrocarbon group of 1 to 10 carbon atoms, R⁴ and R⁸ may bond togetherto form a 5 or 6-membered ring with the carbon atoms to which they areattached, R¹⁰ is a straight, branched or cyclic monovalent hydrocarbonor fluorinated hydrocarbon group of 1 to 15 carbon atoms, A¹ is astraight, branched or cyclic divalent hydrocarbon group of 1 to 10carbon atoms, k¹ is 0 or 1, and n^(1A) is an integer of 0 to 2.

In a second aspect, the invention provides a monomer having the generalformula (2).

Herein R¹ is hydrogen, methyl or trifluoromethyl, R¹⁰ is a straight,branched or cyclic monovalent hydrocarbon or fluorinated hydrocarbongroup of 1 to 15 carbon atoms, R¹¹ is hydrogen or a straight, branchedor cyclic monovalent hydrocarbon group of 1 to 10 carbon atoms, Z¹ formsa C₅-C₁₅ alicyclic group with the carbon atom to which it is attached,and A² is methylene or ethylene.

In a third aspect, the invention provides a polymer comprising recurringunits having the general formula (3a) or (3b).

Herein R¹ to R¹¹, Z¹, A¹, A², k¹, and n^(1A) are as defined above.

The polymer may further comprise recurring units of at least one typeselected from recurring units having the general formulae (4A) to (4E).

Herein R¹ is as defined above, XA is an acid labile group, XB and XC areeach independently a single bond or a straight or branched, divalenthydrocarbon group of 1 to 4 carbon atoms, XD is a straight, branched orcyclic, di- to pentavalent aliphatic hydrocarbon group of 1 to 16 carbonatoms in which a constituent —CH₂— may be substituted by —O— or —C(═O)—,XE is an acid labile group, YA is a substituent group of lactone,sultone or carbonate structure, ZA is hydrogen, a fluoroalkyl group of 1to 15 carbon atoms or a fluoroalcohol-containing group of 1 to 15 carbonatoms, k^(1A) is an integer of 1 to 3, and k^(1B) is an integer of 1 to4.

The polymer may further comprise recurring units of at least one typeselected from sulfonium salt units (d1) to (d3) represented by thefollowing general formula.

Herein R²⁰, R²⁴, and R²⁸ each are hydrogen or methyl; R²¹ is a singlebond, phenylene, —O—R³³—, or —C(═O)—Y—R³³—, wherein Y is oxygen or NHand R³³ is a straight, branched or cyclic C₁-C₆ alkylene or alkenylenegroup or phenylene group, which may contain a carbonyl (—CO—), ester(—COO—), ether (—O—), or hydroxyl moiety; R²², R²³, R²⁵, R²⁶, R²⁷, R²⁹,R³⁰, and R³¹ are each independently a straight, branched or cyclicC₁-C₁₂ alkyl group which may contain a carbonyl, ester or ether moiety,a C₆-C₁₂ aryl group, a C₇-C₂₀ aralkyl group, or a thiophenyl group; Z₀is a single bond, methylene, ethylene, phenylene, fluorinated phenylene,—O—R³²—, or —C(═O)—Z₁—R³²—, wherein Z₁ is oxygen or NH, and R³² is astraight, branched or cyclic C₁-C₆ alkylene or alkenylene group orphenylene group, which may contain a carbonyl, ester, ether or hydroxylmoiety; and M⁻ is a non-nucleophilic counter ion.

In a fourth aspect, the invention provides a process for forming apattern by applying a resist composition comprising the polymer definedabove and an acid generator onto a substrate, baking the composition toform a resist film, exposing the resist film to high-energy radiation todefine exposed and unexposed regions, baking, and applying an organicsolvent developer to the coated substrate to form a negative patternwherein the unexposed region of resist film is dissolved and the exposedregion of resist film is not dissolved.

In another embodiment, the invention provides a process for forming apattern by applying a resist composition comprising the polymercomprising sulfonium salt units (d1) to (d3) onto a substrate, bakingthe composition to form a resist film, exposing the resist film tohigh-energy radiation to define exposed and unexposed regions, baking,and applying an organic solvent developer to the coated substrate toform a negative pattern wherein the unexposed region of resist film isdissolved and the exposed region of resist film is not dissolved.

In a preferred embodiment, the developer comprises at least one organicsolvent selected from the group consisting of 2-octanone, 2-nonanone,2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone,diisobutyl ketone, methylcyclohexanone, acetophenone,methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate,amyl acetate, isoamyl acetate, butenyl acetate, propyl formate, butylformate, isobutyl formate, amyl formate, isoamyl formate, methylvalerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methylpropionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate,ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyllactate, isoamyl lactate, methyl 2-hydroxyisobutyrate, ethyl2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate,benzyl acetate, methyl phenylacetate, benzyl formate, phenylethylformate, methyl 3-phenylpropionate, benzyl propionate, ethylphenylacetate, and 2-phenylethyl acetate.

In a preferred embodiment, the step of exposing the resist film tohigh-energy radiation includes KrF excimer laser lithography ofwavelength 248 nm, ArF excimer laser lithography of wavelength 193 nm,EUV lithography of wavelength 13.5 nm or EB lithography.

In a modified embodiment, the process involves the steps of applying theresist composition onto a substrate, baking the composition to form aresist film, forming a protective film on the resist film, exposing theresist film to high-energy radiation to define exposed and unexposedregions, baking, and applying an organic solvent developer to the coatedsubstrate to form a negative pattern wherein the unexposed region ofresist film is dissolved and the exposed region of resist film is notdissolved.

In a fifth aspect, the invention provides a negative pattern-formingresist composition comprising the polymer defined above, an acidgenerator, and an organic solvent, the resist composition beingdissolvable in an organic solvent developer selected from the same groupas defined above. The acid generator may be omitted when the polymercomprises sulfonium salt units (d1) to (d3).

Advantageous Effects of Invention

A photoresist film comprising a polymer comprising recurring unitsderived from the inventive monomer and an acid generator is used to formimages via positive/negative reversal by organic solvent development. Itdisplays a high dissolution contrast between the unexposed region ofpromoted dissolution and the exposed region of inhibited dissolutionduring organic solvent development. Through exposure and organic solventdevelopment, the photoresist film can form a fine hole pattern at a highprecision of dimensional control, or a trench pattern having highresolution and minimal roughness.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically illustrates in cross-sectional views the patternforming process of the invention, FIG. 1A shows a photoresist filmformed on a substrate, FIG. 1B shows the photoresist film being exposed,and FIG. 1C shows the photoresist film being developed in organicsolvent.

DESCRIPTION OF EMBODIMENTS

In the disclosure, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. The notation(Cn-Cm) means a group containing from n to m carbon atoms per group.

The abbreviations and acronyms have the following meaning.

EB: electron beam

EUV: extreme ultraviolet

PAG: photoacid generator

Mw: weight average molecular weight

Mn: number average molecular weight

Mw/Mn: molecular weight distribution or dispersity

GPC: gel permeation chromatography

PEB: post-exposure bake

EL: exposure latitude

LWR: line width roughness

MEEF: mask error enhancement factor

DOF: depth of focus

It is understood that for some structures represented by chemicalformulae, there can exist enantiomers and diastereomers because of thepresence of asymmetric carbon atoms. In such a case, a single formulacollectively represents all such isomers. The isomers may be used aloneor in admixture.

Monomer

In the first embodiment, the invention provides a monomer having thegeneral formula (1).

Herein R¹ is hydrogen, methyl or trifluoromethyl. R² and R³ are eachindependently a straight, branched or cyclic monovalent hydrocarbongroup of 1 to 10 carbon atoms. R² and R³ may bond together to form aring with the carbon atom to which they are attached. R⁴ to R⁹ are eachindependently hydrogen or a straight, branched or cyclic monovalenthydrocarbon group of 1 to 10 carbon atoms. R⁴ and R⁸ may bond togetherto form a 5 or 6-membered ring with the carbon atoms to which they areattached. R¹⁰ is a straight, branched or cyclic monovalent hydrocarbonor fluorinated hydrocarbon group of 1 to 15 carbon atoms. A¹ is astraight, branched or cyclic divalent hydrocarbon group of 1 to 10carbon atoms, k¹ is 0 or 1, and n^(1A) is an integer of 0 to 2.

Typical straight, branched or cyclic, monovalent C₁-C₁₀ hydrocarbongroups represented by R² to R⁹ are alkyl groups including methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl,cyclohexyl, 2-ethylhexyl, n-octyl, norbornyl, tricyclodecanyl, andadamantyl.

In some embodiments, R² and R³ bond together to form a ring, examples ofwhich are shown below.

Herein and throughout the specification, the broken line designates avalence bond.

In some embodiments, R⁴ and R⁸ bond together to form a 5 or 6-memberedring, examples of which are shown below wherein R¹⁰ is as defined above.

Typical straight, branched or cyclic, monovalent C₁-C₁₀ hydrocarbongroups represented by R¹⁰ are alkyl groups including methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl,2-ethylhexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl,cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl,oxanorbornyl, tricyclo[5.2.1.0^(2,6)]decanyl, and adamantyl.

Typical straight, branched or cyclic, monovalent C₁-C₁₀ fluorinatedhydrocarbon groups represented by R¹⁰ are fluoroalkyl groups, examplesof which are shown below.

Typical straight, branched or cyclic, divalent C₁-C₁₀ hydrocarbon groupsrepresented by A¹ are alkylene groups, examples of which are shownbelow.

A second embodiment of the invention is a monomer having the generalformula (2).

Herein R¹ is hydrogen, methyl or trifluoromethyl. R¹⁰ is a straight,branched or cyclic, monovalent hydrocarbon or fluorinated hydrocarbongroup of 1 to 15 carbon atoms. R¹¹ is hydrogen or a straight, branchedor cyclic monovalent hydrocarbon group of 1 to 10 carbon atoms. Z¹ formsa C₅-C₁₅ alicyclic group with the carbon atom to which it is attached.A² is methylene or ethylene.

Typical straight, branched or cyclic, monovalent C₁-C₁₀ hydrocarbongroups represented by R¹¹ are alkyl groups including methyl, ethyl,propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl,n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl,2-ethylhexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl,cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl,oxanorbornyl, tricyclo[5.2.1.0^(2,6)]decanyl, and adamantyl.

Examples of the C₅-C₁₅ alicyclic group formed by Z¹ are shown below.

Illustrative, non-limiting examples of the monomers having formulae (1)and (2) are given below wherein R¹ is as defined above.

The monomer of formula (1) may be prepared, for example, via steps i) toiv) according to the reaction scheme shown below although the synthesisroute is not limited thereto.

Herein R¹ to R¹⁰, A¹, N^(1A), and k¹ are as defined above. R¹² is astraight, branched or cyclic monovalent hydrocarbon group of 1 to 10carbon atoms. X¹ is a halogen atom, hydroxyl group or —OR¹³ wherein R¹³is methyl, ethyl or a group of the following formula (14).

X² is a halogen atom, hydroxyl group or —OR¹⁴ wherein R¹⁴ is methyl,ethyl or a group of the following formula (15).

Step i) is an addition reaction of a formyl or keto group of oxo-estercompound (5) with hydride reducing/organometallic reagent (6) to formhydroxy-ester compound (7).

The reaction may readily run by a well-known procedure. Suitable hydridereducing reagents include sodium borohydride, lithium borohydride,lithium aluminum hydride, and diisobutylaluminum hydride. Of these,sodium borohydride is preferred for the purpose of selectively reducingonly the formyl or keto group of oxo-ester compound (5). Theorganometallic reagent may be selected from Grignard reagents,organolithium reagents, and organozinc reagents. When the organometallicreagent is used, it is preferred for the purpose of selectivelyeffecting addition reaction to the formyl or keto group of oxo-estercompound (5) that the amount of the organometallic reagent is 1.0 to 2.0moles, specifically 1.0 to 1.2 moles per mole of oxo-ester compound (5).More than 2 moles of the organometallic reagent may result in asubstantial drop of percent yield because addition reaction to an estergroup of oxo-ester compound (5) may also take place to form a noticeableamount of by-product.

The reaction time is determined as appropriate by monitoring thereaction process by thin-layer chromatography (TLC) or gaschromatography (GC) because it is desirable from the yield aspect todrive the reaction to completion. Usually the reaction time is about 30minutes to about 40 hours. Hydroxy-ester compound (7) may be recoveredfrom the reaction mixture by ordinary aqueous work-up. If necessary, thecompound may be purified by standard techniques like distillation,recrystallization and chromatography.

Step ii) is a reaction of hydroxy-ester compound (7) with organometallicreagents (8) and (9) to form diol compound (10).

The reaction may readily run by a well-known procedure. Theorganometallic reagents (8) and (9) may be selected from Grignardreagents, organolithium reagents, and organozinc reagents. Theorganometallic reagents (8) and (9), each one mole equivalent, arereacted in sequence with the ester group of hydroxy-ester compound (7)to form diol compound (10). When R² and R³ on the organometallicreagents (8) and (9) are the same, diol compound (10) can be formed byreacting two mole equivalents of the organometallic reagent with theester group of hydroxy-ester compound (7). This is advantageous forsaving the number of steps.

An appropriate amount of the organometallic reagents (8) and (9) used iseach 2.0 to 10 moles, more preferably 2.0 to 5.0 moles per mole ofhydroxy-ester compound (7). Less than 2.0 moles of the organometallicreagent (8) or (9) may be insufficient to drive addition reaction to theester group, resulting in a substantial drop of percent yield. More than10 moles of the organometallic reagent (8) or (9) may be uneconomicalbecause of an increase of reactant cost and a lowering of pot yield.

The reaction time is determined as appropriate by monitoring thereaction process by TLC or GC because it is desirable from the yieldaspect to drive the reaction to completion. Usually the reaction time isabout 30 minutes to about 40 hours. Diol compound (10) may be recoveredfrom the reaction mixture by ordinary aqueous work-up. If necessary, thecompound may be purified by standard techniques like distillation,recrystallization and chromatography.

Step iii) is a reaction of diol compound (10) with esterifying agent(11) to form hydroxy-ester compound (12).

The reaction may readily run by a well-known procedure. The preferredesterifying agent (11) is an acid chloride of formula (11) wherein X¹ ischlorine or a carboxylic anhydride of formula (11) wherein X¹ is −OR¹³and R¹³ is a group of the following formula (14).

When an acid chloride such as carboxylic acid chloride is used as theesterifying agent (11), the reaction may be conducted in a solventlesssystem or in a solvent (e.g., methylene chloride, acetonitrile, tolueneor hexane) by adding diol compound (10), acid chloride, and a base(e.g., triethylamine, pyridine or 4-dimethylaminopyridine) in sequenceor at the same time, and optional cooling or heating. When a carboxylicanhydride is used as the esterifying agent (11), the reaction may beconducted in a solventless system or in a solvent (e.g., methylenechloride, acetonitrile, toluene or hexane) by adding diol compound (10),carboxylic anhydride, and a base (e.g., triethylamine, pyridine or4-dimethylaminopyridine) in sequence or at the same time, and optionalcooling or heating.

An appropriate amount of diol compound (10) used is 1 to 10 moles, morepreferably 1 to 5 moles per mole of esterifying agent (11). Less than 1mole of diol compound (10) may result in a substantial drop of percentyield because a noticeable amount of a bis-ester compound may be formedby side reaction to esterify both the hydroxyl groups of diol compound(10). More than 10 moles of diol compound (10) may be uneconomicalbecause of an increase of reactant cost and a lowering of pot yield.

The reaction time is determined as appropriate by monitoring thereaction process by TLC or GC because it is desirable from the yieldaspect to drive the reaction to completion. Usually the reaction time isabout 30 minutes to about 40 hours. Hydroxy-ester compound (12) may berecovered from the reaction mixture by ordinary aqueous work-up. Ifnecessary, the compound may be purified by standard techniques likedistillation, recrystallization and chromatography.

Step iv) is a reaction of hydroxy-ester compound (12) with esterifyingagent (13) to form the desire monomer (1).

The reaction may readily run by a well-known procedure. The preferredesterifying agent (13) is an acid chloride of formula (13) wherein X² ischlorine or a carboxylic anhydride of formula (13) wherein X² is −OR¹⁴and R¹⁴ is a group of the following formula (15).

When an acid chloride, typically carboxylic acid chloride such asmethacrylic acid chloride is used as the esterifying agent (13), thereaction may be conducted in a solventless system or in a solvent (e.g.,methylene chloride, acetonitrile, toluene or hexane) by addinghydroxy-ester compound (12), acid chloride, and a base (e.g.,triethylamine, pyridine or 4-dimethylaminopyridine) in sequence or atthe same time, and optional cooling or heating. When a carboxylicanhydride such as methacrylic anhydride is used as the esterifying agent(13), the reaction may be conducted in a solventless system or in asolvent (e.g., methylene chloride, acetonitrile, toluene or hexane) byadding hydroxy-ester compound (12), carboxylic anhydride, and a base(e.g., triethylamine, pyridine or 4-dimethylaminopyridine) in sequenceor at the same time, and optional cooling or heating. When a carboxylicacid of formula (13) wherein X² is hydroxy is used as the esterifyingagent (13), the reaction may be conducted by heating hydroxy-estercompound (12) and carboxylic acid such as methacrylic acid in a solvent(e.g., toluene or hexane) in the presence of an acid catalyst whilewater formed during reaction may be removed out of the system ifdesired. Suitable acid catalysts used herein include mineral acids suchas hydrochloric acid, sulfuric acid, nitric acid and perchloric acid andorganic acids such as p-toluenesulfonic acid and benzenesulfonic acid.When an acid anhydride, typically methacrylic acid anhydride is used asthe esterifying agent (13), the reaction may be conducted in asolventless system or in a solvent (e.g., methylene chloride,acetonitrile, toluene or hexane) by adding hydroxy-ester compound (12),acid anhydride, and a base (e.g., triethylamine, pyridine or4-dimethylaminopyridine) in sequence or at the same time, and optionalcooling or heating.

The reaction time is determined as appropriate by monitoring thereaction process by TLC or GC because it is desirable from the yieldaspect to drive the reaction to completion. Usually the reaction time isabout 30 minutes to about 48 hours. The monomer (1) may be recoveredfrom the reaction mixture by ordinary aqueous work-up. If necessary, themonomer may be purified by standard techniques like distillation,recrystallization and chromatography.

Polymer

A third embodiment of the invention is a polymer orhigh-molecular-weight compound comprising recurring units derived fromthe monomer having formula (1) or (2) defined above.

Specifically, the recurring units derived from the monomer havingformula (1) or (2) are units having the general formula (3a) or (3b).

Herein R¹ is hydrogen, methyl or trifluoromethyl. R² and R³ are eachindependently a straight, branched or cyclic monovalent hydrocarbongroup of 1 to 10 carbon atoms. R² and R³ may bond together to form aring with the carbon atom to which they are attached. R⁴ to R⁹ are eachindependently hydrogen or a straight, branched or cyclic monovalenthydrocarbon group of 1 to 10 carbon atoms. R⁴ and R⁸ may bond togetherto form a 5 or 6-membered ring with the carbon atoms to which they areattached. R¹⁰ is a straight, branched or cyclic monovalent hydrocarbonor fluorinated hydrocarbon group of 1 to 15 carbon atoms. R¹¹ ishydrogen or a straight, branched or cyclic monovalent hydrocarbon groupof 1 to 10 carbon atoms. Z¹ forms a C₅-C₁₅ alicyclic group with thecarbon atom to which it is attached. A¹ is a straight, branched orcyclic divalent hydrocarbon group of 1 to 10 carbon atoms. A² ismethylene or ethylene, k¹ is 0 or 1, and n^(1A) is an integer of 0 to 2.

The inventive polymer serving as base resin in the resist compositionhas, as a side chain, an acid labile tertiary alkyl ester structuresubstituted with an acyloxy group. Since the tertiary alkyl group ishighly lipophilic and the acyloxy group has high affinity to organicsolvent developer, it is expected that the unexposed region of resistfilm is smoothly dissolved during organic solvent development to form anegative pattern. On the other hand, in the exposed region of resistfilm, deprotection reaction takes place under the action of generatedacid, forming highly polar, hydrophilic carboxyl groups which serve tosignificantly reduce the solubility of the resist film in organicsolvent developer so that the exposed region of resist film becomesinsoluble in the developer. Therefore, the resist composition comprisingthe inventive polymer as base resin is expected to achieve a highdissolution contrast of the base resin before and after exposure, andimprovements in resolution and roughness.

The acid labile unit of the polymer must have a structure in which thesubstitution position of the pendant acyloxy is separated at least twocarbons from the quaternary carbon to which the backbone acyloxy isattached. Reference is now made to a polymer of formula (3aa), shownbelow, corresponding to formula (3a) wherein k¹=0 and n^(1A)=0. Thepolymer (3aa) has an acylated 1,3-diol structure which includes thebackbone acyloxy group attached to the quaternary carbon (black circle)and the pendant acyloxy group located at the •-position (separated twocarbons from the black-circled carbon) relative to the quaternarycarbon. The polymer is expected to undergo fast deprotection reactionunder the action of generated acid, which probably entails carbocationformation and ensuing olefin formation.

This is in contrast to a polymer of formula (3c), shown below. Thepolymer (3c) has an acylated 1,2-diol structure which includes thebackbone acyloxy group attached to the quaternary carbon (black circle)and the pendant acyloxy group located at the α-position (separated onecarbon from the black-circled carbon) relative to the quaternary carbon.The polymer (3c) may undergo slow deprotection reaction and haveinsufficient acid reactivity because the electronegative acyloxysubstituent is unstable in vicinity to the carbocation generated byacid.

Herein R¹ to R⁵ and R⁸ to R¹⁰ are as defined above, R^(3ba) and R^(3bb)each are hydrogen or a monovalent hydrocarbon group.

In addition to the units having formula (3a) or (3b), the preferredpolymer may further comprise recurring units of at least one typeselected from recurring units having the general formulae (4A) to (4E).

Herein R¹ is as defined above. XA is an acid labile group. XB and XC areeach independently a single bond or a straight or branched, divalenthydrocarbon group of 1 to 4 carbon atoms. XD is a straight, branched orcyclic, di- to pentavalent aliphatic hydrocarbon group of 1 to 16 carbonatoms in which a constituent —CH₂— may be substituted by —O— or —C(═O)—.XE is an acid labile group. YA is a substituent group of lactone,sultone or carbonate structure. ZA is hydrogen, a fluoroalkyl group of 1to 15 carbon atoms or a fluoroalcohol-containing group of 1 to 15 carbonatoms, k^(1A) is an integer of 1 to 3, and k^(1B) is an integer of 1 to4.

A polymer comprising recurring units of formula (4A) is decomposed underthe action of acid to generate carboxylic acid so that it may turnalkali soluble. The acid labile group XA may be selected from a varietyof such groups. Examples of the acid labile group are groups of thefollowing general formulae (L1) to (L4), tertiary alkyl groups of 4 to20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groupsin which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groupsof 4 to 20 carbon atoms.

Herein R^(L01) and R^(L02) are each independently hydrogen or astraight, branched or cyclic alkyl group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms. R^(L03) is a monovalent hydrocarbongroup of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, whichmay contain a heteroatom such as oxygen, examples of which includestraight, branched or cyclic alkyl groups, substituted forms of suchalkyl groups in which some hydrogen atoms are replaced by hydroxyl,alkoxy, oxo, amino, alkylamino or the like, and similar groups which areseparated by ether oxygen. R^(L04) is a tertiary alkyl group of 4 to 20carbon atoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group inwhich each alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4to 20 carbon atoms, or a group of formula (L1). R^(L05) is an optionallysubstituted, straight, branched or cyclic C₁-C₁₀ alkyl group or anoptionally substituted C₆-C₂₀ aryl group. R^(L06) is an optionallysubstituted, straight, branched or cyclic C₁-C₁₀ alkyl group or anoptionally substituted C₆-C₂₀ aryl group. R^(L07) to R^(L16)independently represent hydrogen or optionally substituted monovalenthydrocarbon groups of 1 to 15 carbon atoms. Letter y is an integer of 0to 6, m is equal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2 m+n isequal to 2 or 3.

In formula (L1), exemplary groups of R^(L01) and R^(L02) include methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl,cyclohexyl, 2-ethylhexyl, n-octyl, and adamantyl.

R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms, which may contain a heteroatom such asoxygen, examples of which include straight, branched or cyclic alkylgroups, substituted forms of such alkyl groups in which some hydrogenatoms are replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or thelike, and similar groups which are separated by ether oxygen.Illustrative examples of the straight, branched or cyclic alkyl groupsare as exemplified above for R^(L01) and R^(L02), and examples of thesubstituted alkyl groups are as shown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may bond together to form a ring with the carbon and oxygenatoms to which they are attached. Each of ring-forming R^(L01), R^(L02)and R^(L03) is a straight or branched alkylene group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms when they form a ring.

In formula (L2), exemplary tertiary alkyl groups of R^(L04) aretert-butyl, tert-amyl, 1,1-diethylpropyl, 2-cyclopentylpropan-2-yl,2-cyclohexylpropan-2-yl, 2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl,2-(adamantan-1-yl)-propan-2-yl, 1-ethylcyclopentyl, 1-butylcyclopentyl,1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl,1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, andthe like. Exemplary trialkylsilyl groups are trimethylsilyl,triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groupsare 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and5-methyl-2-oxooxolan-5-yl.

In formula (L3), examples of the optionally substituted C₁-C₁₀ alkylgroups of R^(L05) include straight, branched or cyclic alkyl groups suchas methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, andbicyclo[2.2.1]heptyl, and substituted forms of such groups in which somehydrogen atoms are replaced by hydroxyl, alkoxy, carboxyl,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio,sulfo or other groups or in which a methylene moiety is replaced by anoxygen or sulfur atom. Examples of optionally substituted C₆-C₂₀ arylgroups include phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, andpyrenyl.

In formula (L4), examples of optionally substituted, straight, branchedor cyclic C₁-C₁₀ alkyl groups and optionally substituted C₆-C₂₀ arylgroups of R^(L06) are the same as exemplified for R^(L05). ExemplaryC₁-C₁₅ monovalent hydrocarbon groups of R^(L07) to R^(L16) includestraight, branched or cyclic alkyl groups such as methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl,n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl,cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyland cyclohexylbutyl, and substituted forms of these groups in which somehydrogen atoms are replaced by hydroxyl, alkoxy, carboxyl,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio,sulfo or other groups. Alternatively, two of R^(L07) to R^(L16) may bondtogether to form a ring with the carbon atom(s) to which they areattached (for example, a pair of R^(L07) and R^(L08), R^(L07) andR^(L09), R^(L08) and R^(L10), R^(L09) and R^(L10), R^(L11) and R^(L12),or R^(L13) and R^(L14) form a ring). Each of R^(L07) to R^(L16)represents a C₁-C₁₅ divalent hydrocarbon group, typically alkylene, whenthey form a ring, examples of which are those exemplified above for themonovalent hydrocarbon groups, with one hydrogen atom being eliminated.Two of R^(L07) to R^(L16) which are attached to vicinal carbon atoms maybond together directly to form a double bond (for example, a pair ofR^(L07) and R^(L09), R^(L09) and R^(L15), or R^(L13) and R^(L15)).

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethyl cyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxy-n-butyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl.

Of the acid labile groups of formula (L4), those groups of the followingformulae (L4-1) to (L4-4) are preferred.

In formulas (L4-1) to (L4-4), the broken line denotes a bonding site anddirection. R^(L41) is each independently a monovalent hydrocarbon group,typically a straight, branched or cyclic C₁-C₁₀ alkyl group, such asmethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Note that R^(L41) is as defined above.

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Note that R^(L41) is as defined above.

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of bicyclo[2.2.1]heptane structure as a substituent group, theremay be contained monomers substituted with an endo-alkyl group asrepresented by the following formulas (L4-1-endo) to (L4-4-endo). Forgood reactivity, an exo proportion of at least 50 mol % is preferred,with an exo proportion of at least 80 mol % being more preferred.

Note that R^(L41) is as defined above.

Illustrative examples of the acid labile group of formula (L4) are givenbelow.

Examples of the tertiary C₄-C₂₀ alkyl groups, trialkylsilyl groups inwhich each alkyl moiety has 1 to 6 carbon atoms, and C₄-C₂₀ oxoalkylgroups, represented by XA, are as exemplified for R^(L04) and the like.

Illustrative examples of the recurring units having formula (4A) aregiven below, but not limited thereto.

Illustrative examples of the recurring units having formula (4B) aregiven below, but not limited thereto.

Illustrative examples of the recurring units having formula (4C) aregiven below, but not limited thereto.

Herein Me stands for methyl.

Illustrative examples of the recurring units having formula (4D) aregiven below, but not limited thereto.

A polymer comprising recurring units of formula (4E) is decomposed underthe action of acid to generate a hydroxyl group so that its solubilityin various solvents may change. The acid labile group XE may be selectedfrom a variety of such groups. Examples of the acid labile group XE aregroups of formulae (L1) to (L4), tertiary alkyl groups of 4 to 20 carbonatoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbonatoms, and oxoalkyl groups of 4 to 20 carbon atoms, like the acid labilegroup XA mentioned above.

Illustrative examples of the recurring units having formula (4E) aregiven below, but not limited thereto.

In a preferred embodiment, the polymer may have further copolymerizedtherein any of recurring units (d1) to (d3) of sulfonium saltrepresented by the following general formulae.

Herein R²⁰, R²⁴ and R²⁸ each are hydrogen or methyl. R²¹ is a singlebond, phenylene, —O—R³³—, or —C(═O)—Y—R³³— wherein Y is oxygen or NH andR³³ is a straight, branched or cyclic C₁-C₆ alkylene or alkenylene groupor phenylene group, which may contain a carbonyl (—CO—), ester (—COO—),ether (—O—) or hydroxyl moiety. R²², R²³, R²⁵, R²⁶, R²⁷, R²⁹, R³⁰, andR³¹ are each independently a straight, branched or cyclic C₁-C₁₂ alkylgroup which may contain a carbonyl, ester or ether moiety, or a C₆-C₁₂aryl group, C₇-C₂₀ aralkyl group, or thiophenyl group. Z₀ is a singlebond, methylene, ethylene, phenylene, fluorinated phenylene, —O—R³²—, or—C(═O)—Z₁—R³²— wherein Z₁ is oxygen or NH and R³² is a straight,branched or cyclic C₁-C₆ alkylene or alkenylene group or phenylenegroup, which may contain a carbonyl, ester, ether or hydroxyl moiety. M⁻is a non-nucleophilic counter ion.

In addition to the foregoing units, the polymer may further compriserecurring units derived from carbon-to-carbon double bond-bearingmonomers other than the above-described ones, for example, substitutedacrylic acid esters such as methyl methacrylate, methyl crotonate,dimethyl maleate and dimethyl itaconate, unsaturated carboxylic acidssuch as maleic acid, fumaric acid, and itaconic acid, cyclic olefinssuch as norbornene, norbornene derivatives, andtetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecene derivatives, unsaturated acidanhydrides such as itaconic anhydride, and other monomers.

The polymer should preferably have a weight average molecular weight(Mw) in the range of 1,000 to 500,000, and more preferably 3,000 to100,000, as measured versus polystyrene standards by GPC usingtetrahydrofuran solvent. Outside the range, there may result an extremedrop of etch resistance, and a drop of resolution due to difficulty togain a dissolution rate difference before and after exposure.

In the polymer, the recurring units derived from the inventive monomerand other monomers are preferably incorporated in the following molarfractions (mol %):

(I) more than 0 mol % to 100 mol %, preferably 5 to 70 mol %, and morepreferably 10 to 50 mol % of constituent units of at least one typeselected from units (3a) and (3b) derived from monomers of formulae (1)and (2);

(II) 0 mol % to less than 100 mol %, preferably 30 to 95 mol %, and morepreferably 50 to 90 mol % of constituent units of at least one typeselected from units (4A) to (4E);

(III) 0 to 30 mol %, preferably 0 to 20 mol %, and more preferably 0 to10 mol % of constituent units of at least one type selected from units(d1) to (d3);

(IV) 0 to 80 mol %, preferably 0 to 70 mol %, and more preferably 0 to50 mol % of constituent units derived from one or more other monomers.

The inventive polymer may be prepared by copolymerization reaction usingthe compound of formula (1) or (2) as a first monomer and polymerizabledouble bond-bearing compounds as second and subsequent monomers, whichprovide recurring units having formulae (4A) to (4E) and (d1) to (d3)and the like. The copolymerization reaction to produce the inventivepolymer may be performed in various modes, preferably radicalpolymerization, anionic polymerization or coordination polymerization.

For radical polymerization, preferred reaction conditions include (a) asolvent selected from among hydrocarbons such as benzene, ethers such astetrahydrofuran, alcohols such as ethanol, and ketones such as methylisobutyl ketone, (b) a polymerization initiator selected from azocompounds such as 2,2′-azobisisobutyronitrile and peroxides such asbenzoyl peroxide and lauroyl peroxide, (c) a temperature of about 0° C.to about 100° C., and (d) a time of about 0.5 hour to about 48 hours.Reaction conditions outside the described range may be employed ifdesired.

For anionic polymerization, preferred reaction conditions include (a) asolvent selected from among hydrocarbons such as benzene, ethers such astetrahydrofuran, and liquid ammonia, (b) a polymerization initiatorselected from metals such as sodium and potassium, alkyl metals such asn-butyl lithium and sec-butyl lithium, ketyl, and Grignard reagents, (c)a temperature of about −78° C. to about 0° C., (d) a time of about 0.5hour to about 48 hours, and (e) a stopper selected from amongproton-donative compounds such as methanol, halides such as methyliodide, and electrophilic compounds. Reaction conditions outside thedescribed range may be employed if desired.

For coordination polymerization, preferred reaction conditions include(a) a solvent selected from among hydrocarbons such as n-heptane andtoluene, (b) a catalyst selected from Ziegler-Natta catalysts comprisinga transition metal (e.g., titanium) and alkylaluminum, Phillipscatalysts of metal oxides having chromium or nickel compounds carriedthereon, and olefin-metathesis mixed catalysts as typified by tungstenand rhenium mixed catalysts, (c) a temperature of about 0° C. to about100° C., and (d) a time of about 0.5 hour to about 48 hours. Reactionconditions outside the described range may be employed if desired.

Resist Composition

The polymer is useful as a base resin in a resist composition,especially for use in organic solvent development process. A furtherembodiment of the invention is a resist composition, typicallychemically amplified resist composition comprising the polymer.Preferably the resist composition comprises the following components:

(A) the inventive polymer as base resin,

(B) an acid generator,

(C) an organic solvent, and optionally,

(D) a nitrogen-containing organic compound and

(E) a surfactant.

It is noted that the acid generator (B) may be omitted when the polymerhas copolymerized therein recurring units (d1), (d2) or (d3).

In some embodiments, the base resin may be a blend of the inventivepolymer with another polymer capable of increasing its dissolution ratein alkaline developer under the action of acid. Suitable other polymersinclude, but are not limited to, (i) poly(meth)acrylate derivatives,(ii) norbornene derivative-maleic anhydride copolymers, (iii)hydrogenated products of ring-opening metathesis polymerization (ROMP)polymers, and (iv) vinyl ether-maleic anhydride-(meth)acrylatederivative copolymers.

With respect to the synthesis of hydrogenated ROMP polymers, referenceshould be made to Examples in JP-A 2003-066612. Examples of thehydrogenated ROMP polymers are shown below, but not limited thereto.

On use of the polymer blend, the inventive polymer and the other polymerare preferably blended in a weight ratio between 100:0 and 10:90, morepreferably between 100:0 and 20:80. If the ratio of the inventivepolymer is less than the range, the resist composition may fail to exertthe desired characteristics. The characteristics of the resistcomposition may be adjusted by changing the blending ratio.

It is also acceptable to use a blend of two or more inventive polymers.The characteristics of the resist composition may be adjusted by using aplurality of inventive polymers.

Typical of the acid generator used herein is a photoacid generator(PAG). The PAG is any compound capable of generating an acid uponexposure to high-energy radiation. Suitable PAGs include sulfoniumsalts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, andoxime-O-sulfonate acid generators. Examples of these PAGs are describedin JP-A 2009-269953, paragraphs [0151] to [0156] (U.S. Pat. No.8,114,571).

It is noted that an acid diffusion controlling function may be providedwhen two or more PAGs are used in admixture provided that one PAG is anonium salt capable of generating a weak acid. Specifically, in a systemusing a mixture of a PAG capable of generating a strong acid (e.g.,fluorinated sulfonic acid) and an onium salt capable of generating aweak acid (e.g., non-fluorinated sulfonic acid or carboxylic acid), ifthe strong acid generated by the PAG upon exposure to high-energyradiation collides with the unreacted onium salt having a weak acidanion, then a salt exchange occurs whereby the weak acid is released andan onium salt having a strong acid anion is formed. In this course, thestrong acid is exchanged into the weak acid having a low catalysis,incurring apparent deactivation of the acid for enabling to control aciddiffusion.

If the PAG capable of generating a strong acid is also an onium salt, anexchange from the strong acid (generated upon exposure to high-energyradiation) to a weak acid as above can take place, but it never happensthat the weak acid (generated upon exposure to high-energy radiation)collides with the unreacted onium salt capable of generating a strongacid to induce a salt exchange. This is because of a likelihood of anonium cation forming an ion pair with a stronger acid anion.

An appropriate amount of PAG added is 0.1 to 40 parts, and morepreferably 0.1 to 20 parts by weight per 100 parts by weight of the baseresin (A) in the resist composition. As long as PAG is up to 40 parts,the resulting resist film has a fully high transmittance and a minimallikelihood of degraded resolution. The PAG may be used alone or inadmixture of two or more. The transmittance of the resist film can becontrolled by using a PAG having a low transmittance at the exposurewavelength and adjusting the amount of the PAG added.

To the resist composition, a compound which is decomposed with an acidto generate another acid, that is, acid amplifier compound may be added.For these compounds, reference should be made to J. Photopolym. Sci. andTech., 8, 43-44, 45-46 (1995), and ibid., 9, 29-30 (1996). Examples ofthe acid amplifier compound include tert-butyl-2-methyl-2-tosyloxymethylacetoacetate and 2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are notlimited thereto. Of well-known PAGs, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior. In the resist composition, an appropriateamount of the acid amplifier compound is up to 2 parts, and especiallyup to 1 part by weight per 100 parts by weight of the base resin.Excessive amounts of the acid amplifier compound make diffusion controldifficult, leading to degradation of resolution and pattern profile.

Component (C) used herein may be any organic solvent as long as the baseresin, acid generator and other components are dissolvable therein.Exemplary organic solvents include ketones such as cyclohexanone andmethyl amyl ketone; alcohols such as 3-methoxybutanol,3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether,ethylene glycol monomethyl ether, propylene glycol monoethyl ether,ethylene glycol monoethyl ether, propylene glycol dimethyl ether, anddiethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone, which may be used aloneor in admixture. Of these, diethylene glycol dimethyl ether,1-ethoxy-2-propanol, PGMEA and mixtures thereof are preferred becausethe acid generator is most soluble therein.

An appropriate amount of the organic solvent used is 200 to 1,000 parts,and especially 400 to 800 parts by weight per 100 parts by weight of thebase resin.

As component (D), nitrogen-containing organic compounds may be usedalone or in admixture. Those compounds capable of suppressing the rateof diffusion when the acid generated by the PAG diffuses within theresist film are useful. The inclusion of such quencher facilitatesadjustment of resist sensitivity and holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure andmitigates substrate poisoning and environment dependence, as well asimproving the exposure latitude and the pattern profile.

Suitable nitrogen-containing organic compounds include primary,secondary, and tertiary aliphatic amines, mixed amines, aromatic amines,heterocyclic amines, nitrogen-containing compounds having carboxylgroup, nitrogen-containing compounds having sulfonyl group,nitrogen-containing compounds having hydroxyl group, nitrogen-containingcompounds having hydroxyphenyl group, alcoholic nitrogen-containingcompounds, amide, imide and carbamate derivatives. Illustrative examplesare described in JP-A 2009-269953, paragraphs [0122] to [0141].

The basic compound is preferably used in an amount of 0.001 to 8 parts,more preferably 0.01 to 4 parts by weight per 100 parts by weight of thebase resin. Less than 0.001 part fails to achieve the desired additioneffect whereas more than 8 parts may lead to a lowering of sensitivity.The preferred nitrogen-containing organic compound is a compound capableof holding down the diffusion rate of acid when the acid generated bythe acid generator diffuses in the resist film. The inclusion of thenitrogen-containing organic compound holds down the diffusion rate ofacid in the resist film, which leads to many advantages includingimproved resolution, minimized sensitivity change following exposure,reduced substrate poisoning and environment dependency, and improvedexposure latitude and pattern profile.

As component (E), nonionic surfactants are preferred. Suitablesurfactants include perfluoroalkylpolyoxyethylene ethanols, fluorinatedalkyl esters, perfluoroalkylamine oxides, perfluoroalkyl EO-additionproducts, and fluorinated organosiloxane compounds. Useful surfactantsare commercially available under the trade names Fluorad FC-430 andFC-431 from Sumitomo 3M, Ltd., Surflon S-141, S-145, KH-10, KH-20, KH-30and KH-40 from Asahi Glass Co., Ltd., Unidyne DS-401, DS-403 and DS-451from Daikin Industry Co., Ltd., Megaface F-8151 from DIC Corp., andX-70-092 and X-70-093 from Shin-Etsu Chemical Co., Ltd. Preferredsurfactants are Fluorad FC-430 from Sumitomo 3M, Ltd., KH-20 and KH-30from Asahi Glass Co., Ltd., and X-70-093 from Shin-Etsu Chemical Co.,Ltd.

Optionally, a polymer may be added to the resist composition of theinvention which will segregate at the top of a coating and functions toadjust a hydrophilic/hydrophobic balance at the surface, to enhancewater repellency, or to prevent low-molecular-weight components fromflowing into or out of the coating when the coating comes in contactwith water or similar liquids. The amount of functional polymer added isas used in resist compositions of this type as long as it does notcompromise the objects of the invention, and is preferably up to 15parts, and more preferably up to 10 parts by weight per 100 parts byweight of the base resin.

Preferred examples of the functional polymer which will segregate at thecoating top include polymers and copolymers comprising fluorinated unitsof one or more types, and copolymers comprising fluorinated units andother units. Illustrative examples of suitable fluorinated units andother units are shown below, but not limited thereto.

The functional polymer which will segregate at the coating top shouldpreferably have a Mw of 1,000 to 50,000, more preferably 2,000 to20,000, as measured by GPC versus polystyrene standards. Outside therange, the polymer may have insufficient surface-modifying effect orcause development defects.

While the resist composition of the invention typically comprises apolymer, acid generator, organic solvent and organic nitrogen-containingcompound as described above, there may be added optional otheringredients such as dissolution inhibitors, acidic compounds,stabilizers, and dyes. Optional ingredients may be added in conventionalamounts so long as this does not compromise the objects of theinvention.

Process

Pattern formation using the resist composition of the invention may beperformed by well-known lithography processes. The process generallyinvolves coating, heat treatment (or prebake), exposure, heat treatment(PEB), and development. If necessary, any additional steps may be added.

The process of forming a negative pattern using an organic solvent asdeveloper is illustrated in FIG. 1. First, the resist composition iscoated on a substrate to form a resist film thereon. Specifically, aresist film 40 of a resist composition is formed on a processablesubstrate 20 disposed on a substrate 10 directly or via an intermediateintervening layer 30 as shown in FIG. 1A. The resist film preferably hasa thickness of 10 to 1,000 nm and more preferably 20 to 500 nm. Prior toexposure, the resist film is heated or prebaked, preferably at atemperature of 60 to 180° C., especially 70 to 150° C. for a time of 10to 300 seconds, especially 15 to 200 seconds.

The substrate 10 used herein is generally a silicon substrate. Theprocessable substrate (or target film) 20 used herein includes SiO₂,SiN, SiON, SiOC, p-Si, α-Si, TiN, WSi, BPSG, SOG, Cr, CrO, CrON, MoSi,low dielectric film, and etch stopper film. The intermediate interveninglayer 30 includes hard masks of SiO₂, SiN, SiON or p-Si, an undercoat inthe form of carbon film, a silicon-containing intermediate film, and anorganic antireflective coating.

Next comes exposure depicted at 50 in FIG. 1B. For the exposure,preference is given to high-energy radiation having a wavelength of 140to 250 nm, EUV having a wavelength of 13.5 nm, and especially ArFexcimer laser radiation of 193 nm. The exposure may be done either in adry atmosphere such as air or nitrogen stream or by immersionlithography in water. The ArF immersion lithography uses deionized wateror liquids having a refractive index of at least 1 and highlytransparent to the exposure wavelength such as alkanes as the immersionsolvent. The immersion lithography involves prebaking a resist film andexposing the resist film to light through a projection lens, with waterintroduced between the resist film and the projection lens. Since thisallows lenses to be designed to a NA of 1.0 or higher, formation offiner feature size patterns is possible. The immersion lithography isimportant for the ArF lithography to survive to the 45-nm node. In thecase of immersion lithography, deionized water rinsing (or post-soaking)may be carried out after exposure for removing water droplets left onthe resist film, or a protective film may be applied onto the resistfilm after pre-baking for preventing any leach-out from the resist filmand improving water slip on the film surface.

The resist protective film used in the immersion lithography ispreferably formed from a solution of a polymer having1,1,1,3,3,3-hexafluoro-2-propanol residues which is insoluble in water,but soluble in an alkaline developer liquid, in a solvent selected fromalcohols of at least 4 carbon atoms, ethers of 8 to 12 carbon atoms, andmixtures thereof. While the protective film must dissolve in the organicsolvent developer, the polymer comprising recurring units derived from amonomer having a 1,1,1,3,3,3-hexafluoro-2-propanol residue dissolves inorganic solvent developers. In particular, protective film-formingmaterials having 1,1,1,3,3,3-hexafluoro-2-propanol residues as describedin JP-A 2007-025634, 2008-003569, 2008-81716, and 2008-111089 readilydissolve in organic solvent developers.

In the protective film-forming composition, an amine compound or aminesalt or a polymer having copolymerized therein recurring unitscontaining an amine group or amine salt may be used. This component iseffective for controlling diffusion of the acid generated in the exposedregion of the photoresist film to the unexposed region for therebypreventing any hole opening failure. Useful protective film materialshaving an amine compound added thereto are described in JP-A2008-003569, and useful protective film materials having an amino groupor amine salt copolymerized are described in JP-A 2007-316448. The aminecompound or amine salt may be selected from the compounds enumerated asthe basic compound to be added to the resist composition. An appropriateamount of the amine compound or amine salt added is 0.01 to 10 parts,preferably 0.02 to 8 parts by weight per 100 parts by weight of the baseresin.

After formation of the photoresist film, deionized water rinsing (orpost-soaking) may be carried out for extracting the acid generator andthe like from the film surface or washing away particles, or afterexposure, rinsing (or post-soaking) may be carried out for removingwater droplets left on the resist film. If the acid evaporating from theexposed region during PEB deposits on the unexposed region to deprotectthe protective group on the surface of the unexposed region, there is apossibility that the surface edges of holes after development arebridged to close the holes. Particularly in the case of negativedevelopment, regions surrounding the holes receive light so that acid isgenerated therein. There is a possibility that the holes are not openedif the acid outside the holes evaporates and deposits inside the holesduring PEB. Provision of a protective film is effective for preventingevaporation of acid and for avoiding any hole opening failure. Aprotective film having an amine compound or amine salt added thereto ismore effective for preventing acid evaporation. On the other hand, aprotective film to which an acid compound such as a carboxyl or sulfogroup is added or which is based on a polymer having copolymerizedtherein monomeric units containing a carboxyl or sulfo group isundesirable because of a potential hole opening failure.

A further embodiment of the invention is a process for forming a patternby applying a resist composition comprising a polymer comprisingrecurring units having formula (3a) or (3b), an acid generator, and anorganic solvent onto a substrate, baking the composition to form aresist film, forming a protective film on the resist film, exposing theresist film to high-energy radiation to define exposed and unexposedregions, baking, and applying a developer to the coated substrate toform a negative pattern wherein the unexposed region of resist film andthe protective film are dissolved and the exposed region of resist filmis not dissolved. The protective film is preferably formed from acomposition comprising a polymer bearing a1,1,1,3,3,3-hexafluoro-2-propanol residue and an amino group or aminesalt-containing compound, or a composition comprising a polymer bearinga 1,1,1,3,3,3-hexafluoro-2-propanol residue and having amino group oramine salt-containing recurring units copolymerized, the compositionfurther comprising an alcohol solvent of at least 4 carbon atoms, anether solvent of 8 to 12 carbon atoms, or a mixture thereof.

With respect to the recurring units having a1,1,1,3,3,3-hexafluoro-2-propanol residue, those monomers having a—C(CF₃) (OH) group, i.e., a carbon atom having CF₃ and OH radicalsbonded thereto are preferably selected among the exemplary monomerslisted for the recurring unit (4D) (some monomers on pages 50 and 51).The amino group-containing compound may be selected from the exemplaryamine compounds (to be added to photoresist compositions) described inJP-A 2008-111103, paragraphs [0146] to [0164]. As the aminesalt-containing compound, salts of the foregoing amine compounds withcarboxylic acid or sulfonic acid may be used.

Suitable alcohols of at least 4 carbon atoms include 1-butyl alcohol,2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol,2-pentanol, 3-pentanol, tert-amyl alcohol, neopentyl alcohol,2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol,cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol,3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol,2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol,3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol,4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol,cyclohexanol, and 1-octanol. Suitable ether solvents of 8 to 12 carbonatoms include di-n-butyl ether, diisobutyl ether, di-sec-butyl ether,di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether, di-t-amylether, and di-n-hexyl ether.

Exposure is preferably performed in an exposure dose of about 1 to 200mJ/cm², more preferably about 10 to 100 mJ/cm². This is followed bybaking (PEB) on a hot plate at 60 to 150° C. for 1 to 5 minutes,preferably at 80 to 120° C. for 1 to 3 minutes.

Thereafter the exposed resist film is developed in a developerconsisting of an organic solvent for 0.1 to 3 minutes, preferably 0.5 to2 minutes by any conventional techniques such as dip, puddle and spraytechniques. In this way, the unexposed region of resist film wasdissolved away, leaving a negative resist pattern 40 on the substrate 10as shown in FIG. 1C. The developer used herein is preferably selectedfrom among ketones such as 2-octanone, 2-nonanone, 2-heptanone,3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone,methylcyclohexanone, acetophenone, and methylacetophenone, and esterssuch as propyl acetate, butyl acetate, isobutyl acetate, amyl acetate,isoamyl acetate, butenyl acetate, propyl formate, butyl formate,isobutyl formate, amyl formate, isoamyl formate, methyl valerate, methylpentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethylpropionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate,propyl lactate, butyl lactate, isobutyl lactate, amyl lactate, isoamyllactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methylbenzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methylphenylacetate, benzyl formate, phenylethyl formate, methyl3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and2-phenylethyl acetate, and mixtures thereof.

At the end of development, the resist film is rinsed. As the rinsingliquid, a solvent which is miscible with the developer and does notdissolve the resist film is preferred. Suitable solvents includealcohols of 3 to 10 carbon atoms, ether compounds of 8 to 12 carbonatoms, alkanes, alkenes, and alkynes of 6 to 12 carbon atoms, andaromatic solvents. Specifically, suitable alkanes of 6 to 12 carbonatoms include hexane, heptane, octane, nonane, decane, undecane,dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane,methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, andcyclononane. Suitable alkenes of 6 to 12 carbon atoms include hexene,heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene,cycloheptene, and cyclooctene. Suitable alkynes of 6 to 12 carbon atomsinclude hexyne, heptyne, and octyne. Suitable alcohols of 3 to 10 carbonatoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol,2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol,2-pentanol, 3-pentanol, tert-amyl alcohol, neopentyl alcohol,2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol,cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol,3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol,2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol,3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol,4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol,cyclohexanol, and 1-octanol. Suitable ether compounds of 8 to 12 carbonatoms include di-n-butyl ether, diisobutyl ether, di-sec-butyl ether,di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether, di-tert-amylether, and di-n-hexyl ether. Suitable aromatic solvents include toluene,xylene, ethylbenzene, isopropylbenzene, tert-butylbenzene, andmesitylene. The solvents may be used alone or in admixture.

Where a hole pattern is formed by negative tone development usingorganic solvent developer, exposure by double dipole illuminations of X-and Y-direction line patterns provides the highest contrast light. Thecontrast may be further increased by combining two dipole illuminationsof X- and Y-direction line patterns with s-polarized illumination. Thesepattern forming processes are described in JP-A 2011-221513.

Like the hole pattern mentioned above, when an isolated space pattern isformed by the positive tone development process in which exposure bringsabout an increase in solubility in alkaline developer, pattern formationmust be done at a lower intensity of incident light than when anisolated line pattern is formed. Thus the intensity contrast of incidentlight between the unexposed and exposed regions is low. This tends toimpose limits on pattern forming abilities such as resolving power,making it difficult to form a resist pattern with high resolution.Unlike the positive tone development process, the negative tonedevelopment process in which exposure brings about a reduction insolubility in alkaline developer is believed advantageous for forming anisolated space pattern. Similarly, the negative tone development processusing organic solvent developer is believed advantageous for forming anisolated space pattern.

EXAMPLE

Synthesis Examples and Examples of the invention are given below by wayof illustration and not by way of limitation. The abbreviation “pbw” isparts by weight. Me stands for methyl. For all polymers, Mw isdetermined versus polystyrene standards by GPC.

Synthesis Example 1

Polymerizable ester compounds within the scope of the invention weresynthesized in accordance with the methods shown below.

Synthesis Example 1-1 Synthesis of Monomer 1

Synthesis Example 1-1-1 Synthesis of Hydroxy-Ester 1a

Sodium borohydride (37.8 g) was dissolved in 300 g of water and 200 g ofTHF. A solution of 284.3 g of Keto-ester 1 in 200 g of THF was addeddropwise to the solution below 30° C. The reaction solution was stirredat room temperature for 1 hour, after which it was ice cooled. To thereaction solution, 200 g of 20% hydrochloric acid aqueous solution wasadded dropwise to quench the reaction. This was followed by standardaqueous workup. The solvent was distilled off, obtaining 275 g (yield95%) of Hydroxy-ester 1a. The compound had a high purity sufficient toeliminate purification and was ready for use in the subsequent step.

¹H-NMR (600 MHz in DMSO-d₆, for only main isomer in a mixture of fourdiastereomers):

δ=4.87 (1H, d), 4.16 (1H, m), 3.58 (3H, s), 2.55 (1H, m), 1.44 (1H, m),1.37-1.80 (6H) ppm

Synthesis Example 1-1-2 Synthesis of Diol 1

A Grignard reagent was prepared from 114.3 g of 1,4-dichlorobutane, 43.8g of metallic magnesium, and 900 g of THF. A solution of 72.1 g of theresulting Hydroxy-ester 1a in 100 g of THF was added dropwise to theGrignard reagent solution below 40° C. The reaction solution was stirredat room temperature for 4 hours, after which it was ice cooled. A mixedaqueous solution of ammonium chloride and 20% hydrochloric acid wasadded dropwise thereto to quench the reaction. This was followed bystandard aqueous workup. After the solvent was distilled off, theproduct was purified by distillation, obtaining 72.4 g (yield 85%) ofDiol 1.

b.p.: 88° C./19 Pa

Synthesis Example 1-1-3 Synthesis of Hydroxy-ester 1b

A solution of 51.1 g of the resulting Diol 1, 60.7 g of triethylamineand 3.7 g of 4-(dimethylamino)pyridine in 100 g of acetonitrile washeated at 40-50° C., to which a solution of 50.6 g of pivaloyl chloridein 20 g of acetonitrile was added dropwise. The reaction solution wasstirred at 60° C. for 1 hour whereupon it was ice cooled. A saturatedsodium hydrogencarbonate aqueous solution was added dropwise thereto toquench the reaction. This was followed by standard aqueous workup. Afterthe solvent was distilled off, the product was purified by distillation,obtaining 72.5 g (yield 95%) of Hydroxy-ester 1b.

b.p.: 76° C./11 Pa

IR (D-ATR): ν=3599, 3512, 2961, 2873, 1725, 1480, 1459, 1397, 1367,1285, 1150, 1032, 995, 970, 937, 845, 772 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆, for only main isomer in a mixture of fourdiastereomers):

δ=5.14 (1H, m), 3.75 (1H, s), 2.05 (1H, m), 1.36-1.83 (14H), 1.09 (9H,s) ppm

Synthesis Example 1-1-4 Synthesis of Monomer 1

A solution of 67.4 g of the resulting Hydroxy-ester 1b, 56.0 g oftriethylamine and 3.2 g of 4-(dimethylamino)pyridine in 100 g ofacetonitrile was heated at 40-50° C., to which 49.9 g of methacryloylchloride was added dropwise. The reaction solution was stirred at 50° C.for 15 hours whereupon it was ice cooled. A saturated sodiumhydrogencarbonate aqueous solution was added dropwise thereto to quenchthe reaction. This was followed by standard aqueous workup. After thesolvent was distilled off, the product was purified by distillation,obtaining 76.9 g (yield 90%) of Monomer 1.

b.p.: 104° C./17 Pa

IR (D-ATR): ν=2960, 2874, 1724, 1712, 1637, 1480, 1452, 1397, 1367,1332, 1304, 1283, 1150, 1032, 1009, 972, 937, 815, 771, 653, 589, 573cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆, for only main isomer in a mixture of fourdiastereomers):

δ=5.87 (1H, s), 5.55 (1H, m), 4.95 (1H, m), 3.04 (1H, m), 2.30 (1H, m),1.79 (3H, s), 1.43-2.04 (14H), 1.11 (9H, s) ppm

Synthesis Example 1-2 Synthesis of Monomer 2

Synthesis Example 1-2-1 Synthesis of Diol 2

Diol 2 was synthesized by the same procedure as Synthesis Example 1-1-2aside from using Hydroxy-ester 2a instead of Hydroxy-ester 1a. Amount169 g, yield 92%.

IR (D-ATR): ν=3315, 2956, 2934, 2856, 1444, 1422, 1365, 1351, 1338,1313, 1288, 1238, 1214, 1197, 1141, 1112, 1066, 1037, 989, 961, 943,930, 904, 845, 817, 654 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆, for only main isomer in a mixture of twodiastereomers):

δ=4.10 (1H, d), 3.79 (1H, m), 3.64 (1H, s), 1.00-1.85 (17H) ppm

Synthesis Example 1-2-2 Synthesis of Hydroxy-ester 2b

Hydroxy-ester 2b was synthesized by the same procedure as SynthesisExample 1-1-3 aside from using 40.0 g of Diol 2 instead of Diol 1. Thereaction solution of Hydroxy-ester 2b was used in the subsequent stepwithout post-treatment.

Synthesis Example 1-2-3 Synthesis of Monomer 2

Methacryloyl chloride, 40.8 g, was added dropwise to the reactionsolution of Hydroxy-ester 2b at 50-60° C., which was stirred at 50° C.for 12 hours. The reaction solution was ice cooled whereupon a saturatedsodium hydrogencarbonate aqueous solution was added to quench thereaction. This was followed by standard aqueous workup. After thesolvent was distilled off, the product was purified by silica gelchromatography, obtaining Monomer 2 (61.8 g, two-step yield 84%).

IR (D-ATR): ν=2954, 2870, 1724, 1713, 1637, 1480, 1448, 1397, 1377,1331, 1303, 1284, 1162, 1096, 1037, 1007, 986, 934, 893, 815 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆, for only main isomer in a mixture of twodiastereomers):

δ=5.92 (1H, m), 5.53 (1H, m), 4.85 (1H, m), 2.25 (1H, m), 3.64 (1H, s),1.82 (3H, m), 1.50-2.03 (16H), 1.13 (9H, s) ppm

Synthesis Example 1-3 Synthesis of Monomer 3

Synthesis Example 1-3-1 Synthesis of Hydroxy-ester 3

A solution of 80.0 g of Diol 2, 44.6 g of pyridine, and 1.0 g of4-(dimethylamino)pyridine in 300 g of THF was ice cooled, to which asolution of 51.0 g of acetic anhydride in 20 g of THF was added dropwisebelow 15° C. The reaction solution was stirred at 10° C. for 1 hour,after which a saturated sodium hydrogencarbonate aqueous solution wasadded dropwise to quench the reaction. This was followed by standardaqueous workup. The solvent was distilled off, obtaining 97.2 g (yield99%) of Hydroxy-ester 3. The compound had a high purity sufficient toeliminate purification and was ready for use in the subsequent step.

IR (D-ATR): ν=3486, 2941, 2867, 1732, 1446, 1371, 1244, 1122, 1037,1021, 993, 956, 931, 907, 896, 853, 823, 705, 606 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆, for only main isomer in a mixture of twodiastereomers):

δ=4.86 (1H, s), 3.74 (1H, s), 1.98 (3H, s), 1.15-1.95 (17H) ppm

Synthesis Example 1-3-2 Synthesis of Monomer 3

Monomer 3 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using Hydroxy-ester 3 instead of Hydroxy-ester 1b.Amount 107.3 g, yield 84%.

IR (D-ATR): ν=2946, 2868, 1733, 1707, 1636, 1448, 1401, 1370, 1331,1302, 1243, 1157, 1097, 1037, 1020, 985, 953, 934, 909, 873, 849, 815,653, 624, 606 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆, for only main isomer in a mixture of twodiastereomers):

δ=5.93 (1H, m), 5.57 (1H, m), 4.87 (1H, m), 2.33 (1H, m), 1.98 (3H, s),1.83 (3H, s), 1.10-2.00 (16M) ppm

Synthesis Example 1-4 Synthesis of Monomer 4

Synthesis Example 1-4-1 Synthesis of Diol 3

Diol 3 was synthesized by the same procedure as Synthesis Example 1-1-2aside from using Hydroxy-ester 4a instead of Hydroxy-ester 1a. Amount297 g, yield 80%.

b.p.: 70° C./20 Pa

¹H-NMR (600 MHz in DMSO-d₆):

δ=4.65 (1H, d), 4.44 (1H, s), 3.90 (1H, m), 1.47-1.74 (10H), 1.06 (3H,d) ppm

Synthesis Example 1-4-2 Synthesis of Hydroxy-ester 4b

Hydroxy-ester 4b was synthesized by the same procedure as SynthesisExample 1-1-3 aside from using Diol 3 instead of Diol 1. Amount 123 g,yield 94%.

b.p.: 65° C./19 Pa

¹H-NMR (600 MHz in DMSO-d₆):

δ=5.04 (1H, m), 4.07 (1H, s), 1.37-1.78 (10H), 1.14 (3H, d), 1.10 (9H,s) ppm

Synthesis Example 1-4-3 Synthesis of Monomer 4

Monomer 4 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using Hydroxy-ester 4b instead of Hydroxy-ester 1b.Amount 129 g, yield 81%.

b.p.: 80° C./19 Pa

IR (D-ATR): ν=2972, 2874, 1723, 1637, 1480, 1454, 1398, 1377, 1333,1284, 1163, 1132, 1049, 937, 816, 771 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆):

δ=5.91 (1H, s), 5.58 (1H, m), 4.87 (1H, m), 2.35 (1H, d), 2.22 (1H, d),2.16 (1H, m), 2.01 (1H, m), 1.81 (3H, s), 1.54-1.70 (6H), 1.10 (3H, d),1.09 (9H, s) ppm

Synthesis Example 1-5 Synthesis of Monomer 5

Synthesis Example 1-5-1 Synthesis of Diol 4

Diol 4 was synthesized by the same procedure as Synthesis Example 1-1-2aside from using methylmagnesium chloride as Grignard reagent andHydroxy-ester 4a instead of Hydroxy-ester 1a. Yield 83%.

Synthesis Example 1-5-2 Synthesis of Hydroxy-ester 5

Hydroxy-ester 5 was synthesized by the same procedure as SynthesisExample 1-1-3 aside from using Diol 4 instead of Diol 1. Yield 96%.

Synthesis Example 1-5-3 Synthesis of Monomer 5

Monomer 5 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using Hydroxy-ester 5 instead of Hydroxy-ester 1b.Yield 79%.

Synthesis Example 1-6 Synthesis of Monomer 6

Monomer 6 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using methacryloyloxyacetyl chloride instead ofmethacryloyl chloride, and pyridine instead of triethylamine and4-(dimethylamino)pyridine. Yield 80%.

Synthesis Example 1-7 Synthesis of Monomer 7

Monomer 7 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using acryloyl chloride instead of methacryloylchloride. Yield 89%.

Synthesis Example 1-8 Synthesis of Monomer 8

Monomer 8 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using α-trifluoromethyacryloyl chloride instead ofmethacryloyl chloride, and pyridine instead of triethylamine and4-(dimethylamino)pyridine. Yield 81%.

Synthesis Example 1-9 Synthesis of Monomer 9

Synthesis Example 1-9-1 Synthesis of Hydroxy-ester 6

Hydroxy-ester 6 was synthesized by the same procedure as SynthesisExample 1-3-1 aside from using Diol 1 instead of Dial 2, trifluoroaceticanhydride instead of acetic anhydride, and only pyridine. Yield 76%.

Synthesis Example 1-9-2 Synthesis of Monomer 9

Monomer 9 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using Hydroxy-ester 6 instead of Hydroxy-ester 1b.Yield 82%.

Synthesis Example 1-10 Synthesis of Monomer 10

Synthesis Example 1-10-1 Synthesis of Hydroxy-ester 7

Hydroxy-ester 7 was synthesized by the same procedure as SynthesisExample 1-3-1 aside from using 4-trifluoromethylcyclohexanecarbonylchloride instead of acetic anhydride. Yield 80%.

Synthesis Example 1-10-2 Synthesis of Monomer 10

Monomer 10 was synthesized by the same procedure as Synthesis Example1-1-4 aside from using Hydroxy-ester 7 instead of Hydroxy-ester 1b.Yield 85%.

Comparative Synthesis Example 1

For comparison with the polymerizable ester compounds of the invention,Comparative Monomer 1 was synthesized in accordance with the followingscheme.

Comparative Synthesis Example 1-1 Synthesis of Diol 5

Diol 5 was synthesized by the same procedure as Synthesis Example 1-1-2aside from using Hydroxy-ester 8a instead of Hydroxy-ester 1a. Amount43.3 g, yield 81%.

b.p.: 59° C./23 Pa

Synthesis Example 1-2 Synthesis of Hydroxy-ester 8b

Hydroxy-ester 8b was synthesized by the same procedure as SynthesisExample 1-1-3 aside from using Diol 5 instead of Diol 1. Amount 63.1 g,yield 93%.

IR (D-ATR): ν=3499, 2987, 2973, 2958, 2906, 2868, 1726, 1699, 1543,1479, 1459, 1446, 1396, 1382, 1369, 1346, 1326, 1289, 1231, 1180, 1105,1082, 1061, 1042, 989, 946, 908, 887, 863, 807, 773 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆):

δ=4.67 (1H, q), 4.30 (1H, s), 1.70 (2H, m), 1.40-1.56 (6H), 1.12 (9H,s), 1.11 (3H, d) ppm

Synthesis Example 1-3 Synthesis of Comparative Monomer 1

Comparative Monomer 1 was synthesized by the same procedure as SynthesisExample 1-1-4 aside from using Hydroxy-ester 8b instead of Hydroxy-ester1b. Amount 71.1 g, yield 96%.

b.p.: 83° C./23 Pa

IR (D-ATR): ν=2975, 2874, 1732, 1717, 1638, 1480, 1455, 1397, 1380,1329, 1304, 1283, 1150, 1067, 1035, 1009, 975, 940, 868, 815, 769 cm⁻¹

¹H-NMR (600 MHz in DMSO-d₆):

δ=5.94 (1H, s), 5.61 (1H, s), 5.55 (1H, q), 1.99 (2H, m), 1.80-1.95 (2H,m), 1.82 (3H, s), 1.70 (2H, m), 1.58 (2H, m), 1.11 (9H+3H) ppm

Monomers 1 to 10 and Comparative Monomer 1 in Synthesis Examples havethe structural formulae shown below.

Synthesis Example 2

Polymers within the scope of the invention were synthesized inaccordance with the methods shown below.

Synthesis Example 2-1 Synthesis of Polymer 1

In a nitrogen atmosphere, 47.0 g of Monomer 1, 26.1 g of4,8-dioxatricyclo[4.2.1.0^(3,7)]nonan-5-on-2-yl methacrylate, 6.9 g of3-hydroxyadamantyl methacrylate, and 3.4 g of dimethyl2,2′-azobisisobutyrate were dissolved in 111 g of methyl ethyl ketone.With stirring under a nitrogen atmosphere, the solution was addeddropwise to 37 g of methyl ethyl ketone at 80° C. over 4 hours. Afterthe completion of dropwise addition, the reaction solution was stirredat 80° C. for 2 hours. The polymerization solution was cooled to roomtemperature, whereupon it was added dropwise to 1,200 g of methanol. Thethus precipitated solids were filtered and dried in vacuum at 50° C. for20 hours, obtaining a polymer in white powder solid form, designatedPolymer 1. Amount 74.4 g, yield 93%.

Polymer 1

a=0.50, b=0.10, c=0.40,

Mw=7,400

Synthesis Examples 2-2 to 2-11 and Comparative Synthesis Examples 2-1 to2-4

Polymers 2 to 11 and Reference Polymers 1 to 4 were synthesized by thesame procedure as Synthesis Example 2-1 except that the type andproportion of monomers were changed. The structure of these polymers isidentified below. Fractions of units incorporated are expressed in molarratio.

Polymer 2

a=0.20, b=0.30, c=0.10, d=0.20, e=0.20,

Mw=7,200

Polymer 3

a=0.50, b=0.10, c=0.20, d=0.20,

Mw=7,300

Polymer 4

a=0.25, b=0.25, c=0.30, d=0.20,

Mw=7,200

Polymer 5

a=0.25, b=0.25, c=0.30, d=0.20,

Mw=7,200

Polymer 6

a=0.30, b=0.20, c=0.30, d=0.20,

Mw=7,200

Polymer 7

a=0.25, b=0.25, c=0.30, d=0.20,

Mw=7,300

Polymer 8

a=0.25, b=0.30, c=0.25, d=0.20,

Mw=7,300

Polymer 9

a=0.25, b=0.35, c=0.35, d=0.05,

Mw=7,100

Polymer 10

a=0.25, b=0.25, c=0.30, d=0.20,

Mw=7,300

Polymer 11

a=0.25, b=0.25, c=0.30, d=0.20,

Mw=7,400

Reference Polymer 1

a=0.50, b=0.10, c=0.40,

Mw=7,400

Reference Polymer 2

a=0.20, b=0.30, c=0.10, d=0.20, e=0.20,

Mw=7,200

Reference Polymer 3

a=0.50, b=0.10, c=0.40,

Mw=7,300

Reference Polymer 4

a=0.25, b=0.30, c=0.25, d=0.20,

Mw=7,300

Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-4 Preparation ofResist Composition

Resist compositions R-1 to R-11 and Comparative Resist compositions R-12to R-15 in solution form were prepared by dissolving a polymer (Polymers1 to 11 or Reference Polymers 1 to 4) as base resin, acid generator,basic compound, and water-repellent polymer in a solvent in accordancewith the formulation of Table 1 and filtering through a Teflon® filterwith a pore size of 0.2 μm. The solvent contained 0.01 wt % ofsurfactant KH-20 (Asahi Glass Co., Ltd.).

The photoacid generator (PAG-1, PAG-2), quencher (Base-1), solvent, andwater-repellent polymer (SF-1) used herein are identified below.

-   PAG-1: triphenylsulfonium    2-(adamantane-1-carbonyloxy)-1,1,3,3,3-pentafluoropropanesulfonate-   PAG-2: 4-tert-butylphenyldiphenylsulfonium    2-(adamantane-1-carbonyloxy)-1,1,3,3,3-pentafluoropropanesulfonate-   Base-1: 2-morpholinoethyl octadecanoate-   PGMEA: 1-methyl-2-methoxyethyl acetate-   CyH: cyclohexanone-   Water-repellent polymer SF-1:

TABLE 1 Water- repellent Resin PAG Quencher polymer Solvent 1 Solvent 2Resist (pbw) (pbw) (pbw) (pbw) (pbw) (pbw) Example 1-1 R-1 Polymer 1PAG-1 Base-1 SF-1 PGMEA CyH (100) (12.5) (1.5) (6.0) (2,000) (500) 1-2R-2 Polymer 2 PAG-2 Base-1 SF-1 PGMEA CyH (100) (12.5) (1.5) (6.0)(2,000) (500) 1-3 R-3 Polymer 3 PAG-1 Base-1 SF-1 PGMEA CyH (100) (12.5)(1.5) (6.0) (2,000) (500) 1-4 R-4 Polymer 4 PAG-1 Base-1 SF-1 PGMEA CyH(100) (12.5) (1.5) (6.0) (2,000) (500) 1-5 R-5 Polymer 5 PAG-1 Base-1SF-1 PGMEA CyH (100) (12.5) (1.5) (6.0) (2,000) (500) 1-6 R-6 Polymer 6PAG-2 Base-1 SF-1 PGMEA CyH (100) (12.5) (1.5) (6.0) (2,000) (500) 1-7R-7 Polymer 7 PAG-1 Base-1 SF-1 PGMEA CyH (100) (12.5) (1.5) (6.0)(2,000) (500) 1-8 R-8 Polymer 8 PAG-1 Base-1 SF-1 PGMEA CyH (100) (12.5)(1.5) (6.0) (2,000) (500) 1-9 R-9 Polymer 9 — Base-1 SF-1 PGMEA CyH(100) (1.5) (6.0) (2,000) (500) 1-10 R-10 Polymer 10 PAG-1 Base-1 SF-1PGMEA CyH (100) (12.5) (1.5) (6.0) (2,000) (500) 1-11 R-11 Polymer 11PAG-1 Base-1 SF-1 PGMEA CyH (100) (12.5) (1.5) (6.0) (2,000) (500)Comparative 1-1 R-12 Reference PAG-1 Base-1 SF-1 PGMEA CyH ExamplePolymer 1 (12.5) (1.5) (6.0) (2,000) (500) (100) 1-2 R-13 ReferencePAG-2 Base-1 SF-1 PGMEA CyH Polymer 2 (12.5) (1.5) (6.0) (2,000) (500)(100) 1-3 R-14 Reference PAG-1 Base-1 SF-1 PGMEA CyH Polymer 3 (12.5)(1.5) (6.0) (2,000) (500) (100) 1-4 R-15 Reference PAG-1 Base-1 SF-1PGMEA CyH Polymer 4 (12.5) (1.5) (6.0) (2,000) (500) (100)

Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-4 ArF LithographyPatterning Test 1: Hole Pattern

On a substrate (silicon wafer), a spin-on carbon film ODL-50 (Shin-EtsuChemical Co., Ltd.) having a carbon content of 80 wt % was deposited toa thickness of 200 nm and a silicon-containing spin-on hard maskSHB-A940 having a silicon content of 43 wt % was deposited thereon to athickness of 35 nm. On this substrate for trilayer process, the resistcomposition (R-1 to R-15) shown in Table 1 was spin coated, then bakedon a hot plate at 100° C. for 60 seconds to form a resist film of 100 nmthick.

Using an ArF excimer laser immersion lithography stepper NSR-610C (NikonCorp., NA 1.30, σ 0.98/0.78, dipole opening 20 deg., azimuthallypolarized illumination, dipole illumination), first exposure wasperformed through a 6% halftone phase shift mask bearing a X-directionline pattern with a pitch of 80 nm and a line width of 40 nm (on-wafersize). Second exposure was then performed through a 6% halftone phaseshift mask bearing a Y-direction line pattern with a pitch of 80 nm anda line width of 40 nm (on-wafer size). After the exposure, the wafer wasbaked (PEB) at the temperature shown in Table 2 for 60 seconds anddeveloped. Specifically, butyl acetate was injected from a developmentnozzle while the wafer was spun at 30 rpm for 3 seconds, which wasfollowed by stationary puddle development for 27 seconds. The wafer wasrinsed with 4-methyl-2-pentanol, spin dried, and baked at 100° C. for 20seconds to evaporate off the rinse liquid.

A hole pattern resulted from image reversal by solvent development. Byobservation under TDSEM S-9380 (Hitachi Hitechnologies, Ltd.), the sizeof 50 holes was measured, from which a size variation 3σ was determined.A smaller value of 3σ is better because it indicates a minimizedvariation of hole size. The results are shown in Table 2.

TABLE 2 PEB Dose Hole size variation temperature (mJ/ 3σ Resist (° C.)cm²) (nm) Example 2-1 R-1 90 37 1.5 2-2 R-2 85 35 1.4 2-3 R-3 90 36 1.62-4 R-4 85 38 1.4 2-5 R-5 90 37 1.3 2-6 R-6 85 35 1.5 2-7 R-7 90 37 1.42-8 R-8 90 37 1.6 2-9 R-9 90 36 1.5 2-10 R-10 90 37 1.6 2-11 R-11 90 381.6 Comparative 2-1 R-12 90 37 3.7 Example 2-2 R-13 85 35 3.8 2-3 R-14100 44 3.9 2-4 R-15 95 40 3.7

Examples 3-1 to 3-11 and Comparative Examples 3-1 to 3-4 ArF LithographyPatterning Test 2: Line-and-Space Pattern and Isolated Space Pattern

On a substrate (silicon wafer), a spin-on carbon film ODL-50 (Shin-EtsuChemical Co., Ltd.) having a carbon content of 80 wt % was deposited toa thickness of 200 nm and a silicon-containing spin-on hard maskSHB-A940 having a silicon content of 43 wt % was deposited thereon to athickness of 35 nm. On this substrate for trilayer process, the resistcomposition (R-1 to R-15) shown in Table 1 was spin coated, then bakedon a hot plate at 100° C. for 60 seconds to form a resist film of 100 nmthick. Using an ArF excimer laser immersion lithography scanner NSR-610C(Nikon Corp., NA 1.30, σ 0.98/0.78, 4/5 annular illumination), patternexposure was performed through Mask A or B described below.

Mask A is a 6% halftone phase shift mask bearing a line pattern with apitch of 100 nm and a line width of 50 nm (on-wafer size). Afterexposure through Mask A, the wafer was baked (PEB) at the temperatureshown in Table 3 for 60 seconds and developed. Specifically, butylacetate was injected from a development nozzle while the wafer was spunat 30 rpm for 3 seconds, which was followed by stationary puddledevelopment for 27 seconds. The wafer was rinsed with4-methyl-2-pentanol, spin dried, and baked at 100° C. for 20 seconds toevaporate off the rinse liquid. As a result, the unexposed regions whichhad been masked with Mask A were dissolved in the developer, that is,image reversal took place to form a line-and-space (L/S) pattern with aspace width of 50 nm and a pitch of 100 nm.

Mask B is a 6% halftone phase shift mask bearing a line pattern with apitch of 200 nm and a line width of 45 nm (on-wafer size). Afterexposure through Mask B, the wafer was baked (PEB) at the temperatureshown in Table 3 for 60 seconds and developed. Specifically, butylacetate was injected from a development nozzle while the wafer was spunat 30 rpm for 3 seconds, which was followed by stationary puddledevelopment for 27 seconds. The wafer was rinsed with4-methyl-2-pentanol, spin dried, and baked at 100° C. for 20 seconds toevaporate off the rinse liquid. As a result, the unexposed regions whichhad been masked with Mask B were dissolved in the developer, that is,image reversal took place to form an isolated space pattern (referred toas “trench pattern”, hereinafter) with a space width of 35 nm and apitch of 200 nm.

Evaluation of Sensitivity

As an index of sensitivity, the optimum dose (Eop, mJ/cm²) whichprovided an L/S pattern with a space width of 50 nm and a pitch of 100nm on exposure through Mask A was determined. The results are shown inTable 3. A smaller value indicates higher sensitivity.

Evaluation of Exposure Latitude (EL)

The exposure dose which provided an L/S pattern with a space width of 50nm±10% (i.e., 45 nm to 55 nm) on exposure through Mask A was determined.EL (%) is calculated from the exposure doses according to the followingequation:EL(%)=(|E1−E2|/Eop)×100wherein E1 is an exposure dose which provides an L/S pattern with aspace width of 45 nm and a pitch of 100 nm, E2 is an exposure dose whichprovides an L/S pattern with a space width of 55 nm and a pitch of 100nm, and Eop is the optimum exposure dose which provides an L/S patternwith a space width of 50 nm and a pitch of 100 nm. The results are shownin Table 3.Evaluation of Line Width Roughness (LWR)

An L/S pattern was formed by exposure in the optimum dose (determined inthe sensitivity evaluation) through Mask A. By observation under TDSEMS-9380 (Hitachi Hitechnologies, Ltd.), the space width was measured atlongitudinally spaced apart 10 points, from which a 3-fold value (3σ) ofstandard deviation (σ) was determined and reported as LWR. The resultsare shown in Table 3. A smaller value of 3σ indicates a pattern having alower roughness and more uniform space width.

Evaluation of Mask Error Enhancement Factor (MEEF)

An L/S pattern was formed by exposure in the optimum dose (determined inthe sensitivity evaluation) through Mask A with the pitch fixed and theline width varied. MEEF was calculated from variations of the mask linewidth and the pattern space width according to the following equation:MEEF=(pattern space width)/(mask line width)−bwherein b is a constant. The results are shown in Table 3. A valuecloser to unity (1) indicates better performance.Evaluation of Depth-of-Focus (DOF) Margin

The exposure dose and DOF which ensured to form a trench pattern with aspace width of 35 nm on exposure through Mask B were defined as theoptimum exposure dose and the optimum DOF, respectively. The depth (μm)over which focus was changed that could form a resist pattern with aspace width of 35 nm±10% (i.e., 31.5 nm to 38.5 nm) was determined andreported as DOF. The results are shown in Table 3. A larger valueindicates a smaller change of pattern size with a change of DOF andhence, better DOF margin.

TABLE 3 PEB temper- Eop Re- ature (mJ/ EL LWR DOF sist (° C.) cm²) (%)(nm) MEEF (μm) Example 3-1 R-1 90 25 18 3.4 2.1 0.18 3-2 R-2 85 28 153.1 1.9 0.15 3-3 R-3 90 26 17 3.2 2.0 0.14 3-4 R-4 85 28 16 3.3 1.9 0.153-5 R-5 90 25 15 3.3 2.1 0.16 3-6 R-6 85 27 18 3.2 2.2 0.17 3-7 R-7 9025 17 3.1 2.3 0.16 3-8 R-8 90 26 16 3.4 2.2 0.15 3-9 R-9 90 25 16 3.32.0 0.14 3-10 R-10 90 25 18 3.2 2.1 0.17 3-11 R-11 90 25 17 3.3 2.3 0.16Compar- 3-1 R-12 90 40 11 7.2 4.2 0.05 ative 3-2 R-13 85 28 12 6.8 4.40.07 Example 3-3 R-14 100 33 10 7.3 4.4 0.06 3-4 R-15 95 28 10 6.9 4.50.05

As seen from the results of Tables 2 and 3, the resist compositionswithin the scope of the invention form negative patterns via organicsolvent development with the advantages of hole size uniformity,improved exposure latitude, LWR and MEEF of L/S patterns, and improvedDOF margin of trench patterns. The compositions are advantageouslyapplicable to the organic solvent development process.

Japanese Patent Application No. 2013-032716 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

The invention claimed is:
 1. A monomer having the general formula (2):

wherein R¹ is hydrogen, methyl or trifluoromethyl, R¹⁰ is a straight,branched or cyclic monovalent hydrocarbon or fluorinated hydrocarbongroup of 1 to 15 carbon atoms, R¹¹ is hydrogen or a straight, branchedor cyclic monovalent hydrocarbon group of 1 to 10 carbon atoms, Z¹ formsa C₅-C₁₅ alicyclic group with the carbon atom to which it is attached,and A² is methylene or ethylene.
 2. The monomer of claim 1 which isselected from the group consisting of those having the followingformulae:

wherein R¹ is as defined above.
 3. A polymer comprising recurring unitshaving the general formula (3b):

wherein R¹ is hydrogen, methyl or trifluoromethyl, R² and R³ are eachindependently a straight, branched or cyclic monovalent hydrocarbongroup of 1 to 10 carbon atoms, R¹⁰ is a straight, branched or cyclicmonovalent hydrocarbon or fluorinated hydrocarbon group of 1 to 15carbon atoms, R¹¹ is hydrogen or a straight, branched or cyclicmonovalent hydrocarbon group of 1 to 10 carbon atoms, Z¹ forms a C₅-C₁₅alicyclic group with the carbon atom to which it is attached, and A² ismethylene or ethylene.
 4. The polymer of claim 3, further comprisingrecurring units of at least one type selected from recurring unitshaving the general formulae (4A) to (4E):

wherein R¹ is as defined above, XA is an acid labile group, XB and XCare each independently a single bond or a straight or branched, divalenthydrocarbon group of 1 to 4 carbon atoms, XD is a straight, branched orcyclic, di- to pentavalent aliphatic hydrocarbon group of 1 to 16 carbonatoms in which a constituent —CH₂— may be substituted by —O— or —C(═O)—,XE is an acid labile group, YA is a substituent group of lactone,sultone or carbonate structure, ZA is hydrogen, a fluoroalkyl group of 1to 15 carbon atoms or a fluoroalcohol-containing group of 1 to 15 carbonatoms, k^(1A) is an integer of 1 to 3, and k^(1B) is an integer of 1 to4.
 5. The polymer of claim 3, further comprising recurring units of atleast one type selected from sulfonium salt units (d1) to (d3)represented by the following general formula:

wherein R²⁰, R²⁴, and R²⁸ each are hydrogen or methyl; R²¹ is a singlebond, phenylene, —O—R³³—, or —C(═O)—Y—R³³—, wherein Y is oxygen or NHand R³³ is a straight, branched or cyclic C₁-C₆ alkylene or alkenylenegroup or phenylene group, which may contain a carbonyl (—CO—), ester(—COO—), ether (—O—), or hydroxyl moiety; R²², R²³, R²⁵, R²⁶, R²⁷, R²⁹,R³⁰, and R³¹ are each independently a straight, branched or cyclicC₁-C₁₂ alkyl group which may contain a carbonyl, ester or ether moiety,a C₆-C₁₂ aryl group, a C₇-C₂₀ aralkyl group, or a thiophenyl group; Z₀is a single bond, methylene, ethylene, phenylene, fluorinated phenylene,—O—R³²—, or —C(═O)—Z₁—R³²—, wherein Z₁ is oxygen or NH, and R³² is astraight, branched or cyclic C₁-C₆ alkylene or alkenylene group orphenylene group, which may contain a carbonyl, ester, ether or hydroxylmoiety; and M⁻ is a non-nucleophilic counter ion.
 6. The polymer ofclaim 3 wherein the recurring units having the general formula (3b) isone derived from a monomer selected from the group consisting of thosehaving the following formulae:

wherein R¹ is as defined above.
 7. A process for forming a pattern byapplying a resist composition comprising the polymer of claim 3 and anacid generator onto a substrate, baking the composition to form a resistfilm, exposing the resist film to high-energy radiation to defineexposed and unexposed regions, baking, and applying an organic solventdeveloper to the coated substrate to form a negative pattern wherein theunexposed region of resist film is dissolved and the exposed region ofresist film is not dissolved.
 8. The process of claim 7 wherein thedeveloper comprises at least one organic solvent selected from the groupconsisting of 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone,4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone,methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate,butyl acetate, isobutyl acetate, amyl acetate, isoamyl acetate, butenylacetate, propyl formate, butyl formate, isobutyl formate, amyl formate,isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate,ethyl crotonate, methyl propionate, ethyl propionate, ethyl3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyllactate, isobutyl lactate, amyl lactate, isoamyl lactate, methyl2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethylbenzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzylformate, phenylethyl formate, methyl 3-phenylpropionate, benzylpropionate, ethyl phenylacetate, and 2-phenylethyl acetate.
 9. Theprocess of claim 7 wherein the step of exposing the resist film tohigh-energy radiation includes KrF excimer laser lithography ofwavelength 248 nm, ArF excimer laser lithography of wavelength 193 nm,EUV lithography of wavelength 13.5 nm or EB lithography.
 10. The processof claim 7, comprising the steps of applying the resist composition ontoa substrate, baking the composition to form a resist film, forming aprotective film on the resist film, exposing the resist film tohigh-energy radiation to define exposed and unexposed regions, baking,and applying an organic solvent developer to the coated substrate toform a negative pattern wherein the unexposed region of resist film isdissolved and the exposed region of resist film is not dissolved.
 11. Aprocess for forming a pattern by applying a resist compositioncomprising the polymer of claim 5 onto a substrate, baking thecomposition to form a resist film, exposing the resist film tohigh-energy radiation to define exposed and unexposed regions, baking,and applying an organic solvent developer to the coated substrate toform a negative pattern wherein the unexposed region of resist film isdissolved and the exposed region of resist film is not dissolved.
 12. Anegative pattern-forming resist composition comprising the polymer ofclaim 3, an acid generator, and an organic solvent, the resistcomposition being dissolvable in a developer selected from the groupconsisting of 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone,4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone,methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate,butyl acetate, isobutyl acetate, amyl acetate, isoamyl acetate, butenylacetate, propyl formate, butyl formate, isobutyl formate, amyl formate,isoamyl formate, methyl valerate, methyl pentenoate, methyl crotonate,ethyl crotonate, methyl propionate, ethyl propionate, ethyl3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyllactate, isobutyl lactate, amyl lactate, isoamyl lactate, methyl2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethylbenzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzylformate, phenylethyl formate, methyl 3-phenylpropionate, benzylpropionate, ethyl phenylacetate, and 2-phenylethyl acetate.
 13. Anegative pattern-forming resist composition comprising the polymer ofclaim 5 and an organic solvent, the resist composition being dissolvablein a developer selected from the group consisting of 2-octanone,2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone,3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone,methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate,amyl acetate, isoamyl acetate, butenyl acetate, propyl formate, butylformate, isobutyl formate, amyl formate, isoamyl formate, methylvalerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methylpropionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate,ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, amyllactate, isoamyl lactate, methyl 2-hydroxyisobutyrate, ethyl2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate,benzyl acetate, methyl phenylacetate, benzyl formate, phenylethylformate, methyl 3-phenylpropionate, benzyl propionate, ethylphenylacetate, and 2-phenylethyl acetate.